Biassing devices

ABSTRACT

A biassing device for biassing an actuator member which is longitudinally movable between two limiting positions to the direction in which it has been moved beyond a position intermediate the two positions. The device comprises a pair of link members pivotally engaging the actuator member at the ends of a transverse pin, and a bellcrank lever pivoted at its elbow on a fixed pivot and pivotally engaging the link members at one of its arms. Movement of the other arm of the bellcrank lever in response to movement of the actuator member is referred to a helical compression spring coaxially arranged on the actuator member by a sleeve formed with slots through which the pin projects to engage the link members.

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United States Patent 1 3,595,095

Inventors Brie" "Wills Ream 3,394,614 7/1968 Zeidler 74 512 a d J h H s, th of Stafford. 776,521 12/1904 Levin 74 100 England 1,011,555 12/1911 Archie 74/100 1 1 pp 807,549 1,481,951 1/1924 Asbury 74/102 [22I I Filed Mar. 17, I969 2,671,632 3/1954 Palmer 74/100 [45] Patented July 27, 1971 [73] Assignee The English Electric Company Limited r' 'f' O f London England Ass/slant Examiner-Wesley S. Ratl1|ff,.lr. [32] Priority Man 15 1968 Attarneys-Misegades & Douglas, Keith Misegades and [33] Great Britain George R. Douglas.Jr. 1 3 12637/68 V v ABSTRACT: A biassing device for biassing an actuator [54] BIASSING DEVICES member which islongitudinallv movable between two limiting positions to the direction in WhlCh 1t has been moved beyond a 7 Claims, 2 Drawing Flgs.

posltion 1ntermed1ate the two positions. The device comprises [52] US. Cl 74/l00 a i f link members pivotally engaging the actuator 21/44 member at the ends ofa transverse pin, and a bellcrank lever [50] Field of Search 74/100, i d at it elbow on a fixed pivot and pivotally engaging the 12; 200/1 3, 63 link members at one ofits arms. Movement of the other arm of R f the bellcrank lever in response to movement of the actuator e member is referred to a helical compression spring coaxially UNITED STATES PATENTS arranged on the actuator member by a sleeve formed with 1,495,063 5/1924 Bailhe 74/513 slots through which the pin projects to engage the link mem- 2,111,686 3/1938 Warren 74/513 bers.

geese BllASSllNG DEVlClES direction the member is moved beyond a position intermediate its two limiting positions; in particular when the member is in one of its limiting positions, the associated biassing device biases it to that position.

A particular application of 'the invention is to electrical switchgear. It is known in electrical switchgear to provide a biassing arrangement having a helical compression spring by which a movable contact is biassed towards, separately, its open and closed positions.

The spring is arranged with its axis generally perpendicular to the line of movement of an actuator rod to which the contact is connected and which is longitudinally movable to effect the desired contact movement. The actuator rod has two limiting positions corresponding to the open and closed positions of the contact, and movement of the rod between these limiting positions has the effect of first compressing the spring and then, when the rod has passedbeyond an intermediate position, allowing the spring to expand.

Thus the spring first acts against the rod movement until the rod reaches its intermediate position, and thereafter assists the rod movement. The rod is therefore always biassed to the direction in which it has been moved beyond the intermediate position, and when in one of its limiting positions is biassed towards that position. Usually the spring is pivoted at its end remote from the actuator rod and therefore can follow the rod movement without bending.

By reason of the generally perpendicular arrangement of the spring with respect to the actuator rod, however, such a biassing arrangement is somewhat bulky and is therefore unsatisfactory where space is at a premium. This is particularly so if the actuator rod is at the electrical potential of its associated contact and an insulating clearance must be provided between the spring and neighboring parts of the switchgear structure.

It is an object of the present invention to provide a biassing device which may provide the same biassing effect as the biassing arrangement described above, but which inherently requires less overall space, at least transversely of the longitudinally movable member.

According to the present invention, a biassing device for an elongate member which is longitudinally movable in relation to fixed structure between two limiting positions comprises a bellcrank iever having its elbow pivotally mounted on the fixed structure for pivotal movement of the lever in a plane parallel to the said member, and having a first lever arm extending alongside of the said member and a second lever arm extending towards and transversely of the said member, a spring means acting between the second lever arm and the fixed structure with a line of action substantially parallel to the said member in such a direction that the first lever arm is biassed thereby towards the said member, and a link extending in a plane parallel to said member from a first pivotal engagement with the said member to a second pivotal engagement with the first lever arm such that, owing to the biassing of the first lever arm, the link applies to the said member a force which biases the said member towards whichever of the two limiting positions it happens to be occupying, the force reversing its direction as the member passes an intermediate position during movement from one to the other of the limiting positions.

According to a preferred feature of the invention, the spring means comprises a compression spring and a coupling means is provided for referring the movement of the second lever arm to the spring means. Preferably the coupling means comprises a sleeve which is coaxiallv arranged on the said member and which is formed with a longitudinal slot through which projects a pin forming part of the first pivotal engagement. Advantageously, the second lever arm is formed with a cam face for engagement with the coupling means.

In order-that the invention' may be more fully understood, a biassing device in accordance'with the invention will now be described, by way of example'and with reference to the accompanying drawing, in its application to the biassing of the actuator rod for actuating the'movable contact of an electrical switchgear. ln'the drawings FIG. '1 is a side elevationof the biassing device in central vertical section, and V i l FIG. 2 is a sectional view of the line ll ll of FlG. l.

Referring now to the drawing, the actuator rod is indicated by the reference numeral and is arranged for reciprocatory movement along its own axis by a pneumatic actuator not shown.

A sleeve ll surround the rod 10 with a clearance, and is formed withtwo longitudinal and diametrically opposed slots 12. Through these slots project the ends of a pin 13 which is carried by the rod 10 ina hole bored diametrically through the rod.

A compression spring M coaxially surrounds the rod 10 between one end face ofthe sleeve Ill and anend wall 16 of the generally cylindrical fixed structure 17 of the biassing device. I

Two identical link members 118 are located one on each side of the sleeve 11. Each link member. has one end pivotally secured to a respective one of the projecting ends of the pin 13, so that each link member 18 is capable of pivotal movement about the pin axis. The other ends of the link members carry between them a'further pin 19 which pivotally engages a hook formed at the end of an arm 20 ofa bellcrank lever 21.

The lever 21 is pivoted at its elbow on a pivot pin 24 having its ends secured in the fixed structure 17 (as shown in FIG. 2) and'has its other arm formed with'a cam-face 22. This face abuts the end face 23 of the sleeve 11 remote from the spring M and maintains the spring partly compressed at all times, as will become apparent from the following description.

The rod position shown in the drawing is such that the associated movable contact is spaced apartlfrom its associated fixed contact further leftward movement of the rod is prevented by the pneumatic actuator which is at one end of its stroke. in this position the rod is biassed to the left, i.e. the contact open" position, by the spring M. In providing this bias the spring acts on the rod via the sleeve Ill and the linkage formed by the members 21 and 18.

When it is desired to close the contacts, the rod it) is progressively moved to the right by the actuator.

During an initial part of the movement the link members 18 force the lever 2ll to rotate in a clockwise direction about the pivot pin 24. The sleeve 111 is therefore forced to the left by the cam face 22, so further compressing the spring M. It will be understood that during this time the spring M opposes the rod movement and tends to force it back to its contact open position. it will also be understood that the relative movement of the sleeve ill and pin 13 is accommodated by the slots 12.

Further rightward movement of the rod then brings the pin 13 immediately beneath the pin l9 (i.e. in the same radial plane with respect of the rod. At this intermediate position of the rod, the biassing device produces no biassing force although the spring M has been considerably compressed by the previous clockwise movement of the bellcrank lever Zli.

After the pin 13 has passed to the right of the pin 19, further movement of the rod allows the lever 21 to return towards its original position by rotation in an anticlockwise direction under the action of the spring 14. The spring is therefore allowed partially to relax, and in so doing aids the movement of the rod to the right.

Eventually the rod reaches the end of its travel at a contacts closed" position determined by the other end of the actuator stroke. The spring M is still partly compressed so that the rod is firmly held in this position by the biassing device until the contacts next require to be opened and the biassing device accordingly operates in the reverse procedure to that described above.

it will be noted that the biassing device shown and described is a compact and robust arrangement of which the greatest radial dimension is approximately that of the structure 17 itself. (At the intermediate position of the actuator rod the arm 20 of the bellcrank lever 21 projects a small way beyond the confines of the structure 17, as can be understood from FIG. 2). The device is therefore particularly of value where space is at a premium because, even if the device is at or near the system voltage, adequate insulating clearance to neighboring earthed equipment can be provided without making the device unduly bulky.

Because of its compact nature the device shown and described overcomes one of the disadvantages of biassing devices which have previously been used for the actuator rods effecting contact engagement and disengagement in electrical switchgear. These previous devices have also comprised a helical spring, but the spring has been arranged with its axis generally perpendicular to the rod axis with the result that the devices have been rather bulky and have been unsatisfactory where space is at a premium, particularly when substantial insulating clearances have had to be provided.

The invention is in no way limited in application to electrical switchgear; it has many applications where two-directional biassing of a longitudinally movable member is required.

In a modification of the device shown and described the spring 14 and sleeve 11 are omitted and replaced by a tension spring which is arranged coaxially of the rod to the right of the lever 21. One end of the spring is secured to the lever arm which in the drawing carries the cam face 22; the other end of the spring is attached to a remote part of the fixed structure 17 to the right of the drawing.

We claim:

1. A biassing device for an elongate member which is longitudinally movable in relation to fixed structure between two limiting positions, comprising a bellcrank lever having its elbow pivotally mounted on the fixed structure for pivotal movement of the lever in a plane parallel to the said member, and having a first lever arm extending alongside of the said member and a second lever arm extending towards and transversely of the said member,

a spring means acting between the second lever arm and the fixed structure with a line of action substantially parallel to the said member in such a direction that the first lever arm is biassed thereby towards the said member,

and a link extending in a plane parallel to the said member from a first pivotal engagement with the said member to a second pivotal engagement with the first lever arm such that, owing to the biassing of the first lever arm, the link applies to the said member a force which biases the said member towards whichever of the two limiting positions it happens to be occupying, the force reversing its direction as the member passes an intermediate position during movement from one to the other of the limiting positions.

2. A biassing device according to claim 1, wherein the spring means comprise a compression spring, and including coupling means for referring the movement of the second lever arm to the spring means.

3. A biassing device according to claim 2, wherein the fixed structure is substantially tubular closely surrounding the compression spring and having an internal transverse abutment against which the spring acts.

4. A biassing device according to claim 3, wherein the bellcrank lever lies within the substantially tubular fixed structure when the said member is in either of its limiting positions, and the said structure has a longitudinal opening permitting the first lever arm to lift when the said member is moved through its intermediate position.

5. A biassing device according to claim 4, wherein the elbow of the bellcrank lever is pivotally mounted on a pin extending across the said opening.

6. A biassing device according to claim 4, wherein the spring is coaxially arranged on the said member, the coupling means comprises a sleeve which is also coaxially arranged on the said member and is formed with at least one longitudinal slot, and the said first pivotal engagement comprises a pin which projects through the said slot between the said member and the said link.

7. A biassing device according to claim 6, wherein the second lever arm is formed with a cam face for engagement with the coupling means. 

1. A biassing device for an elongate member which is longitudinally movable in relation to fixed structure between two limiting positions, comprising a bellcrank lever having its elbow pivotally mounted on the fixed structure for pivotal movement of the lever in a plane parallel to the said member, and having a first lever arm extending alongside of the said member and a second lever arm extending towards and transversEly of the said member, a spring means acting between the second lever arm and the fixed structure with a line of action substantially parallel to the said member in such a direction that the first lever arm is biassed thereby towards the said member, and a link extending in a plane parallel to the said member from a first pivotal engagement with the said member to a second pivotal engagement with the first lever arm such that, owing to the biassing of the first lever arm, the link applies to the said member a force which biases the said member towards whichever of the two limiting positions it happens to be occupying, the force reversing its direction as the member passes an intermediate position during movement from one to the other of the limiting positions.
 2. A biassing device according to claim 1, wherein the spring means comprise a compression spring, and including coupling means for referring the movement of the second lever arm to the spring means.
 3. A biassing device according to claim 2, wherein the fixed structure is substantially tubular closely surrounding the compression spring and having an internal transverse abutment against which the spring acts.
 4. A biassing device according to claim 3, wherein the bellcrank lever lies within the substantially tubular fixed structure when the said member is in either of its limiting positions, and the said structure has a longitudinal opening permitting the first lever arm to lift when the said member is moved through its intermediate position.
 5. A biassing device according to claim 4, wherein the elbow of the bellcrank lever is pivotally mounted on a pin extending across the said opening.
 6. A biassing device according to claim 4, wherein the spring is coaxially arranged on the said member, the coupling means comprises a sleeve which is also coaxially arranged on the said member and is formed with at least one longitudinal slot, and the said first pivotal engagement comprises a pin which projects through the said slot between the said member and the said link.
 7. A biassing device according to claim 6, wherein the second lever arm is formed with a cam face for engagement with the coupling means. 